X-ray generator



OCL'19Q1943. M J, ZUNlCK 2,332,422

x-RAY GENERATOR Filed March 28,k 1942 JJ .47 51 a5 Patented Oct. 19, 1943 eral Electric X-Ray Corporation, corporation of New York Chicago, Ill., a

Application Marcil 2a, 1942, semi No. 436,705

2 Claims.

My invention'rclates in general to electronics and has more particular reference to an X-ray generator having an anode providing an electron target comprising target material electroplated as a thtn film on a suitable support.

An important object of the present invention resides in providing an anode having an electro# plated electron target; a further object being to provide an anode Vfor an X-ray generator having a target surface comprising a thin film of metal plated von a suitable base by electrochemical action, whereby the target comprises a deposit of substantially' pure metal particularly Well suited for analysis of materials by X-ray dif-v fraction. i

Another important object isto provide an `X` ray tube for the analysis of materials by'diffraction, the tube having an electron target of substantially pure metal capable of producing Xrays of known characteristics for use in diffraction analysis.

The foregoing and numerous'other important objects, advantages and inherent functions of the invention will beco-me'lapparent as the same is more fully understood from the following description, which, taken in connection with the accompanying drawing, discloses a preferred embodiment of the invention.

Referring to the drawing:

vFigure l is a side view, partially sectionalized,

lmaterial of the target, and hence its characteriisticV line spectrum, is known,v otherwise, the

lines caused by the target material in the spec-y Ytrograph ofthe material being examined `may rbe mistaken for `linesfsupposedly caused by the r material under examination.

The choice cfa proper target material for X- `ray diffractionA analysis depends toa greatexf tent upon the type of specimen',beingexamined,

lthe particular examination technique employed,

of the spectrum Ycharacteristics of the ltarget and hence of the X-rays produced by 'the generator,

` It will be apparent that, in ordery to facilitate X-f of an X-ray tube embodying my present inven- Figures 2 and 3 are sectional enlarged views taken substantially along the line 2-1-2 in Figure l l vto 'show preferred forms of anode structure embodying the invention.

Analysis of materials may be accomplished by exposing the lmaterial to be analyzed to X-rays and observing the X-ray diffraction characteristicsof the material on a sensitive screen or film.

The radiation of X-rays from ageneratorv comprises a continuous, or whitef spectrum; the wave length and intensity distribution of which depends largely upon the operating potential of the generator and upon the characteristic line spectrum of the X-ray target material employed in the generator, every target material having its own characteristic line spectrum which is independent of the operating potential ofthe generator above a minimum voltage, which minimum voltage is also -characteristic ofthe particular target material involved. Any target material may, of course, be employed for X-ray diffraction analysis, provided that the raydiiraction analysis, it-is 'desirableto provide generatorsy having identical characteristics `so that examination technique and procedure need not be altered orfmodied to'suitleach individualA X-ray source. It' is, however,l difcult tok produce .X-ray generators having` identical spec#VV trum characteristics', even where the generators include'. targets of identicalmaterial, for the Areason that the inclusion of impurities in the material ofthe target within the range of contamination tolerated in so-called commercially pure' materials, may alter the .spectrum characteristics of commercially identical targets to an appreciable extent.y l o In order to facilitate examination of materials by X-ray diffraction, I provide a target of de-- sired material in substantially pure condition so vide an anode comprising a base of suitable m'a-` v terial for supporting the target, and I apply the target as a thin lm of material by electroplating the target material on the base.

To illustrate the invention, I have shown 'on the rdrawingv an X-ray tube H comprising an anode I3 and a cathode I5 in facing relationship enclosed within an hermetically sealed land evacuated envelope Il, having suitable electrical connections extending' through thel envelope for supplying'the anode and cathode with electrical power from a suitable external source. y The cathode l5 may comprise a head I9 supported and sealed upon a re-entrant envelope portion comprising a hollow stem 2l. Conductors 23 for energizing the electron `ernittingla ment 25x/nay' extend through the stemv `2l Lhe cathode end of the tube may be fitted WithvaV ferrule 28 carrying a base 29 for connecting the conductors 23 with a suitable external source of power for energizing the filament 25 for electron emission.

It will be noted that the filament is of elongated character and is supported in a groove 21 formed in the cathode head whereby electrons emitted by the laments, when energized, will be focused upon the facing or target end 3I of the anode. The anode, near its target remote end, is formed with a shoulder to which is sealed a disk or washer 33 having an annular edge forming glass-to-metal seal 35 rWitlithe re-entrant portion 4I of the envelope, the anode having an extension 43 projecting outwardly of i. i

the envelope through the sealmember 33 and being tted with inlet and outlet conduits `45 for the circulation of a cooling fluid into the anode adjacent the target end thereof for cooling the same.

The envelope I1 preferably, though not essentially, comprises llead glass and is formed with conical embossments fitted with window-panes 41 of lime glass, beryllium, or other suitable window-pane material lsubstantially transparent to X-rays, the windows 41 being located on the envelope opposite the target end of the anode in position to project X-rays emanating from the target end of the anode outwardly of the envelope. The cathode head also 'is preferably provided with a skirt y49 encircling the target end of th'e anode andformed with openings I for the transmission of useful X-ray beams from the anode to and through the Vwindows 41. The tube also ispreferably enclosed in an annular sleeve 53, which may comprise split parts suitably clamped together around the window portion of the envelope, the sleeve 53 being provided with openings 55 for receiving th'e window carrying envelope projections. If desired, the sleeve 53 may be formed of material opaque to X-rays for thepurpose of confining therein all X-rays except the beams which emanate from the anode through theopenings 5| in the cathode skirt, th'e windows 4.1, and the sleeve openings 55.

The anode I3 comprises a base of suitable material such as copper for supporting an electron target thereon at the target end 3I of the anode. I may employ any suitable .target material, such as chromium, cobalt, nickel, iron, copper, manganese, or other metal susceptible of being applied to the metal anode base by an electroplating operation.

The base of the anode`I3 may first be finished to desired size and shape and its target end 3l th'en treated in a suitable electroplating solutionfcr a sufficient period of time to accomplish a deposit of target material of desired thickness in the form of a target layer 51 on the target end of the anode. The plated anode may then be buried or otherwise polished prior to the assembly of the anode in operating posi tion in the generator.

While it is exceedingly di'icult, if not impossible, to obtain electron targets -in "pure condition, uncontaminated by infusion of other materials, where the anode is fitted with a target comprising a preformed block of target material, I find that, by applying the target material in accordance with my present invention, 4a target of pure metal is obtained; and, as a consequence, generators fitted with -anodes having targets of like material, applied in accordance with the teachings of my present invention, produce X-rays having identical spectral characteristics. Furthermore, since the target material is applied as a thin film, there is little, if any tendency of the material Within the target area to fracture, curl up, or otherwise deteriorate in service, since the thin target layer is able to dissipate heat rapidly into the body or base of the anode I3; and consequently there is no wide temperature diierential between the base attach'ed and electron receiving surfaces of the target layer, and no appreciable internal stress set up within the layer, when the generator is in operation.

While the target layer 51 may be applied directly upon the base of the anode I3, I find it desirable, particularly in plating chromium as a target material on a copper base, to apply a foundation coating 59 of material such as gold or platinum, the target material 51 being then plated as a layer upon the previously plated layer 59. The foundation coating may be applied in any suitable manner, as by the electroplating process or other procedure for filming the foundation material on the base to form the layer 53. This multiple layer arrangement is of advantage Where it is desired to employ an extremely thin target layer 51 or Where the target material, as plated, has a tendency to be minutely porous. Where 'the material of the layer 51 has a tendency towards even slight porosity when plated, the material of the base may become effective through pores in the layer 51 and thus interfere with the spectral characteristics of X-rays generated at the anode. The effects of porosity of the target layer 51 may, of course, be obviated by making the layer suiliciently thick to preclude any possibility of pores therein. By applying a foundation layer of gold 59 or platinum, or other material having X-ray Spectral characteristics that will not interfere with the X-ray spectrum of the target material in the layer 5T, theeiects of pores for spectrographic purposes is nulliiied for the reason that gold or platinum, if exposed to electron bombardment, of the velocity normally employed in the operation of X-ray generators, will not have their characteristic radiation excited, and hence if exposed within the target area, as through pores in the layer 51, have no appreciable effect upon the spectral characteristics of the resulting X-rays. It is thought that the invention and its numerous attendant advantages will be fully understood from the foregoing description, and it is obvious that numerous changes may be made in the forni, `construction and arrangement of the several parts Without departing from the spirit or scope of the invention, or sacricing any of its attendant advantages, the form herein disclosed being a preferred embodiment for the purpose of .illustrating the invention.

The invention is hereby claimed as follows: 1. An X-ray generator comprising a sealed envelope, an electron emitting cathode and a co-operating anode providing an electron target in said envelope, said cathode being formed and positioned to direct electrons upon said target for the generation of X-rays at the target, said anodeccomprising a base forming a target surface coated witha film of metal forming a base layer and Ametallic target material electroplated as a thin layer upon said coated target surface, the metal forming said base layer having X-ray spectorgraphic characteristics which do not interfere Y with the X-ray spectrum of the target material and the target material comprising one of the metals of the class consisting of cobalt, nickel, iron and manganese.

2. An Xr-ray generator comprising a sealed envelope an electron emitting cathode and a co-operating anode providing an electron target in said envelope, said cathode being formed and positioned to direct electrons upon said target 10 for the generation of X-rays at the target, said anode comprising a base forming a target surface, a film of gold forming a base layer coated on said target surface, and metallic target material electroplated upon said base layer, said target material comprising one of the metals of the class consisting of cobalt, nickel, iron and manganese.

MICHAEL J. ZUNICK. 

